1. Field of the Invention
The present invention relates to a liquid discharge apparatus that can maintain a high cleaning effect when cleaning a liquid discharge head where nozzle arrays for discharging liquid are formed, and a method of controlling the liquid discharge apparatus.
2. Description of the Related Art
A liquid discharge apparatus such as an inkjet printer forms an image on a recording sheet by discharging ink from nozzle arrays that are formed at a liquid discharge head. For this reason, if an image is formed while a liquid discharge surface (a portion where the nozzle arrays are formed) of the liquid discharge head is contaminated or liquid or dirt is attached to the liquid discharge surface, printing quality deteriorates. In particular, if ink, which has a color different from the colors of existing ink (liquid), may flow back from nozzles in the case of an inkjet printer that manages full color, the color of the ink is mixed to the colors of the existing ink (liquid), so that mixed color ink is discharged during printing. As a result, image quality deteriorates.
Accordingly, in the past, various techniques, which clean a liquid discharge surface of a liquid discharge head, have been proposed in order to prevent the deterioration of printing quality. For example, a rubber blade method, which slides a slightly hard rubber blade over the liquid discharge surface while pushing the rubber blade against the liquid discharge surface, removes contaminations, standing ink, thickened or solidified ink, and the like, which are attached to the liquid discharge surface, by wiping them off. As a result, the discharge of ink is restored or discharge performance is stabilized.
However, ink, etc. attached to the liquid discharge surface is apt to remain in the rubber blade method, so that a sufficient cleaning effect may not be obtained. In particular, since a line inkjet printer includes a line head where head chips for discharging ink (liquid) are arranged side by side so as to correspond to a printing width, an ink discharge surface (liquid discharge surface) is wide. For this reason, it is difficult to uniformly push the rubber blade against the entire ink discharge surface, so that wiping is not sufficient. Further, among line heads, there is a line head where stepped portions are formed on an ink discharge surface. In the case of this kind of line head, it may not be possible to remove ink that remains at the stepped portions.
FIGS. 12A and 12B are cross-sectional views showing a state where a line head 120 is being cleaned by a rubber blade method in the related art, as seen from the side surface.
As shown in FIG. 12A, a rubber blade method makes a rubber blade 141 come into contact with an ink discharge surface 121 of a line head 120 and moves the rubber blade 141 along the ink discharge surface 121 in an arrangement direction of nozzles like an arrow, thereby wiping off standing ink and the like that are attached to the ink discharge surface 121. Therefore, it is necessary that the rubber blade 141 uniformly comes into contact with the ink discharge surface 121 without a gap.
Meanwhile, if a stepped portion is formed on the ink discharge surface 121 as shown in FIG. 12B, a gap is formed between a corner of the stepped portion and the rubber blade 141 that comes into press contact with the ink discharge surface 121 and is bent. Accordingly, the rubber blade 141 does not come into contact with the corner of the stepped portion. For this reason, it may not be possible to wipe off residual ink attached to the gap or dirt and foreign materials that are pushed to the corner of the stepped portion by the movement of the rubber blade 141.
Accordingly, there is known a wiping roller method that slides or rotationally moves not the rubber blade 141 but a cleaning roller (not shown), which is made of a foam material excellent in water adsorbability, on an ink discharge surface 121, so as to adsorb residual ink attached to the corner of the stepped portion. According to this method, the porous foam forming the cleaning roller is recessed so as to correspond to the stepped portion, so that a gap may not be formed at the corner of the stepped portion. Further, since a pore (cell) formed in the porous foam generates a capillary force, it may be possible to clean the ink discharge surface while adsorbing standing ink and the like attached to the ink discharge surface 121 by the capillary force.
However, in the wiping roller method, water of the ink, which is once adsorbed in a flexible porous foam forming the cleaning roller and held in the porous foam, is hardly evaporated. Accordingly, time is necessary for drying the porous foam. For this reason, whenever cleaning is performed, water is adsorbed in the porous foam. As a result, the porous foam is saturated with water, so that the adsorbability of the porous foam deteriorates. In addition, if the porous foam is saturated with water, ink held in the cleaning roller is transferred to the ink discharge surface 121. For this reason, there is a concern that the ink discharge surface 121 is contaminated. For this reason, in order to cope with these problems, the outer diameter of the cleaning roller should be increased or the cleaning roller should be replaced at regular intervals.
Accordingly, there is known a cleaning cloth method that uses not a cleaning roller but a tape-shaped cleaning cloth. In this method, a cleaning cloth is automatically wound around a reel while an action surface of a cleaning cloth is pressed against an ink discharge surface 121 by a plane. For this reason, it may be possible to typically wipe off the ink discharge surface 121 with a fresh portion of the cleaning cloth.
Further, there is also known a technique where an elastic roller is rotatably disposed around an axis parallel to an arrangement direction of nozzles and an endless cleaning belt is provided on the outer periphery of the roller. In this cleaning belt method, a cleaning belt for cleaning nozzles comes into press contact with the ink discharge surface 121 due to the elastic action of the roller. Further, the roller is rotationally driven by a motor and the cleaning belt positioned at a position facing the nozzles is rotated, so that it may be possible to remove contaminations from the ink discharge surface 121.
These techniques are disclosed in JP-A-11-78034 and JP-A-5-92575.